1. Field of the Invention
The present invention relates to a lightweight and easy to operate device for bending expansion loops in cable--particularly coaxial cable--which must be bent in a manner which reduces stressing, cutting or wrinkling of the cable so as to prevent signal leakage from the cable.
2. Description of the Related Art
Devices for bending expansion loops in coaxial cables are known. For example, U.S. Pat. Nos. 3,824,835, 3,855,838, and 4,569,219 show devices used to form expansion loops in a length of coaxial cable. These patents describe the reasons why expansion loops are necessary in coaxial cable: to compensate for temperature expansion and contraction of the cable when it is suspended from poles by way of a support cable (sometimes also referred to as a "lasher cable"). The devices for bending expansion loops shown in each of these patents, however, require complicated mechanisms for forming the expansion loops, including ratcheted or geared central bending shoes. The complicated nature of the bending mechanisms shown in these patents, and the structural rigidity of the frame needed to support such mechanisms, can result in these devices being undesirably heavy. Such devices can weigh up to 30 pounds, which makes them difficult to maneuver by an operator working at the top of a pole, and therefore raises the risk that the operator will instead bend the loop by hand. Hand-bent expansion loops increase the chances that the cable will be damaged during bending, and that the loop will be non-uniform and therefore exhibit undesirable expansion and contraction characteristics. In addition, in many of the type of devices shown in these patents, it is necessary for the operator to hold the bender in one hand while bending the cable with the other. This procedure increases the risk that the bender will be dropped, endangering other workers, and makes the bending operation itself much more difficult. In addition, in the prior art devices described above, the complicated nature of the bending mechanisms made the devices difficult to operate, and could lead to premature operator fatigue--again, increasing the risk that the bending device will not be used by an operator and that an improper or damaged expansion loop will be made.
Another type of prior art device which has been used to produce expansion loops in coaxial cable is a simple frame or form. U.S. Pat. No. 4,569,219, at col. 1, lines 35-41. describes a wooden form with an arcuate surface around which a cable is bent by hand. A device of this type, manufactured of plastic and containing a single groove on the arcuate surface for receiving the coaxial cable as it is bent and a groove on the top surface for aligning the expansion loop with the support cable, has been sold under the trade name MULLEN BENDER.RTM.. As discussed in U.S. Pat. No. 4,569,219, devices of this type--although lightweight--are disadvantageous because of the considerable manual effort required to bend the cable around the form to produce an expansion loop. In addition, this type of device requires the operator to support the form in one hand while at the same time bending the cable around the form with the other hand. This operation makes use of such a form difficult for a single operator, particularly one operating at a great height, and increases the chances of premature operator fatigue and that the frame or form will be dropped.